Early human hand evolution is a good test of how climbing and tool-making can coexist in one body. A 2025 Science Advances study scanned finger bones of two fossil hominins, Australopithecus sediba and Homo naledi, and found signs of both climbing and manipulation in their hands.
Source: Science Advances, 2025, study led by Samar Syeda and colleagues at the American Museum of Natural History.
What the researchers did
Instead of only measuring the outer shape of bones, the team used 3D scanning to examine bone thickness inside the finger bones. Bone remodels under repeated stress, so internal thickness can record how a hand was habitually used. Fingers that often grip branches should look different from fingers used mainly for precise handling.
| Species | Approximate age | What the finger bones suggest |
|---|---|---|
| Australopithecus sediba | About 2 million years | Strong grasping for climbing, together with human-like thumb features for handling objects |
| Homo naledi | About 300,000 years | Climbing-type finger loading alongside features linked to precise manipulation |
Scanning has another advantage. It does not damage the fossils, and it lets researchers compare many bones with the same method, including those of chimpanzees, gorillas and modern humans.
The key finding
The two species show a mix. Both retain features that suit grasping and hanging, and both have traits associated with controlled handling of objects. Climbing and manipulation did not replace each other in a simple sequence. They appear to have coexisted in the same hands.
Why this changes the usual story
A familiar textbook line says that walking upright freed the hands for tools. This study suggests the picture was more gradual. Even after hominins were walking upright, some still climbed, and their hands kept features for both jobs. The sample is small, and only two species are examined, so the result should not be stretched across all early hominins.
Background for the answer
Human hands differ from ape hands in several well-known ways. The thumb is longer relative to the fingers and fully opposable, the fingers are shorter and straighter, and the hand can perform both a power grip, used to hold a hammer, and a precision grip, used to hold a pen. Apes have long curved fingers suited to hanging from branches. Fossil hands often sit between these two patterns, which is why they attract so much attention.
A good answer links form to function. Name the feature, say what it allows, and then say what the fossil evidence adds.
The two species are also far apart in time. Australopithecus sediba lived about two million years ago in South Africa, while Homo naledi is much younger, so a mixed hand was not a brief transitional stage. It persisted for a very long time in different lineages.
Evidence and inference
The internal bone thickness is measured evidence. The reading of it as a record of climbing and manipulation is an inference, based on comparison with living apes and humans. It does not mean that the species made tools, which needs separate archaeological evidence.
Using it in UPSC Mains
In the exam, keep the new study to one or two lines of an answer on erect posture or hand evolution. It signals current awareness without taking space from the core anatomy.
Use this under Paper I, Section 1.5, which covers the comparative anatomy of humans and apes and the skeletal changes that came with erect posture. It gives a recent example for answers on the hand, alongside the classic points about the opposable thumb and the precision grip.
Practise with the PYQs Skeletal Differences Between Humans and Chimpanzees (2014) and Skeletal Changes Due to Erect Posture (2016). More are in the Human Evolution and Primatology PYQs. Place this topic in a complete revision plan with the Anthropology Optional complete guide.
Sources
Syeda et al., finger bone structure in Australopithecus sediba and Homo naledi, Science Advances (2025).